I have been thinking quite a bit about this lately. I am in the process of building my own music software applications. This is actually allowing me to leave MacOS since Ableton was previously the anchor for me. I can now build tools that are more geared towards what I always wanted in Rust much like DHH was talking about in that talk.
I could sell some of my tools I built but I am on the fence about it. As a few others have said, there is still work and taste that goes into those tools that some might not want to put the effort into. However, there will be an increasing number of people who just build bespoke tools for themselves. That's probably ok. There's a market for both.
The most important thing now (and maybe always) is distribution. If anyone can build something then it ultimately comes down to your ability to market, build trust and provide support at 2:30 AM. That's hard to do when you're a one person shop. Software is an ongoing operational commitment if you make it your business.